Top ten safety issues for power batteries include: 1. Battery safety 2. Group safety 3. Battery management 4. Design safety 5. Charging safety 6. Use safety 7. Safety warning 8. Daily maintenance 9. Safety protection 10. Safety level Division. This collation is to select three core issues from 10 questions for discussion and to propose solutions for this group, as follows:
1. Battery core solutionGroup C: Standardization of battery cells and battery modules
Several aspects can be improved through standardization:
(1) In terms of design, focus on the design of the battery core and focus on it;
(2) In terms of production equipment, the degree of standardization of equipment will be correspondingly higher, and the iteration of equipment enterprise products will be faster;
(3) Continuous improvement and experience promotion. Through standardization, the experience of excellent equipment suppliers and spare parts suppliers can be promoted to the industry, thus improving the safety technology level of the battery industry as a whole.
Group D: Standardization of batteries
Standardization of batteries can reduce duplication of low-level labor. The standardization of the battery itself greatly improves the safety performance of the battery core. More manufacturers make the same standard battery core, the cost of the battery core will decrease, and the safety will be improved. From the perspective of urgency and achievability, it is more urgent and easier to achieve.
2. Group security solutionGroup D: Thermal management design is very important for battery safety
In terms of group security, the thermal management design is good, the heat is balanced, and although the BMS has a small current balance, the voltage difference caused by the temperature difference between different batteries can be equalized because the battery is the temperature of the electrochemical linist equation. The positive electrode is positively correlated, the negative electrode is negatively correlated, and the voltage difference is larger when the positive electrode is reduced by the negative electrode, so the temperature has a large influence on its voltage.
Of course, the welding process is also an important aspect. The welding process is different, which will lead to an unbalanced rise in internal resistance, so it is better to improve its group safety from these dimensions.
Group F: Electrical management and thermal management of PACK
The safety problem ultimately comes down to the battery module. Using the system theory method to consider the safety of the battery and PACK, the BMS must perform accurate detection, control and early warning for each battery core.
At the same time, we must not only consider the safety of the battery, but ignore its life. We must ensure the safety of the battery and the life of the battery as much as possible. If there is no good life, the reason for using the lithium battery is lost.
3. Battery management solutionsGroup C: BMS Security Policy
The battery system is graded and the corresponding safety objectives are established, and the safety strategy for measurement, identification, and processing is determined and verified according to the target. If the industry concentrates on doing this, it can improve battery safety in the short term.
Group F: BMS for cell detection, control, and early warning
We should fundamentally think that the lithium battery itself is unsafe, and it is guilty to infer that it is an unsafe energy device. It needs to be controlled by BMS, and the external heating is out of control, and the fire extinguishing mechanism and device are timely. Love, immediately start the fire extinguisher to extinguish the fire.
4. Design security solutionGroup F: Scientific and reasonable system design, production process control
Various battery materials and battery structures have advantages and disadvantages, but the degree of influence on safety is different. As long as the design is scientific and manufacturing is precise, a power battery with acceptable safety can be manufactured to a certain extent.
5. Charging safety solutionGroup A: Increase battery quick check function on charging device
When the vehicle is charged 80%-90%, the current is detected. The DC memory changes to find out the inconsistencies in the battery pack and achieve the purpose of rapid medical examination.
Before the PACK leaves the factory, it will do a large current pulse charging and discharging, do a large current pulse charging at the end of the charging, and make a large current pulse discharge at the end of the discharge. By this method, the battery combination is inconsistent. The place to find out, may be the problem of the battery, the connection may be a problem, or the data line may be a problem, these large current pulses will obviously show some abnormalities.
Apply this method to the client because the client has no detectable means other than charging the stub.
Group D: Current pulse detection of the battery at the initial stage of charging
For the currents of the SOE and SOH charged by different batteries, the current is pulsed and detected at the initial stage of charging, and an inconsistency is found, and a safety alarm is issued in advance. Because the battery PACK is normal temperature at the initial stage of charging, the temperature of the battery PACK may have risen by 10° or 15° at the end of charging, resulting in the battery voltage being unbalanced, so it may be less error to detect its inconsistency during equalization. .
In addition, the BMS is diagnosed and detected in real time, and the three parties of the vehicle, the charging pile and the power grid are coordinated to fully guarantee the charging safety.
6. Use a safe solutionGroup E: How to ensure personnel safety in the case of single thermal runaway
(1) There are some mature design methods for delaying thermal runaway:
The fireproof material is used to make fireproof and heat insulation treatment on the fireproof structure. As can be seen in the design of Tesla, it can certainly delay the process of thermal runaway to some extent, delaying the thermal runaway of the monomer to the whole process of thermal runaway.
(2) In order to increase the escape time of personnel, take the initiative to do some testing:
Smoke detection, chemical composition detection, heat detection, etc., through the detection of early monomer thermal runaway, and give drivers and passengers an alarm to remind people to escape.
(3) Do the restriction processing:
Can not let the driver to use according to the normal power, through the limited power mode, so that the car has a certain power, but the power is very weak, you can stop by the side to do the treatment.
(4) Add fire extinguishing equipment:
At present, the national standard for electric buses is promoting the addition of fire-extinguishing devices. Adding fire-extinguishing devices may have advantages and disadvantages, because now the design of the battery box will increase the explosion-proof valve. If a large amount of gas or aerogel is injected, it will cause internal pressure to increase, possibly Breaking the explosion-proof valve will bring another problem.
If the monomer is accidentally detected, it may cause the whole battery to be scrapped. If the gas, liquid or semi-gel substance is not harmful to the battery, it is better to choose this material. Can achieve this effect.
(5) Vehicle design:
In the design of the whole vehicle, it is necessary to increase the safety escape device. The electric vehicle is different from the traditional one. The battery is the only power source for the electric vehicle. In the case of thermal runaway, if the power is cut off by means of power cut, the door may not open. Therefore, it is also a viable option to increase the escape door or other escape device that can be quickly and conveniently opened in the design of the whole vehicle.
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